Sorry about posting the log. I performed a system reboot on the macbook air, and XBMC worked fine after that.

I'm not sure that the log at this point would contain any information that would indicate why XBMC stopped responding. Perhaps there was a low memory condition that it didn't handle well? Other applications seem to work fine.

If it happens again, I will post the full log and the crash report (generated by doing a force quit) to pastebin.com and I will put the link here.